A cluster of reports of hypersensitivity reactions among patients who switched from carvedilol (immediate release formulation, referred to hereafter as carvedilol) to carvedilol extended release was received during the initial post-launch period of carvedilol extended release. In follow up to this observation, product labeling for both agents was updated and a nested case control study was subsequently conducted to examine the risk of serious hypersensitivity reactions i.e. anaphylactic reaction and/or angioedema among patients who used carvedilol extended release compared to carvedilol and separately compared to other long acting beta(β)-blockers. This proposed analysis is an update to the previously conducted analysis using the same database, LabRx, now containing 2 additional years of data, which should provide a larger number of carvedilol extended release exposed subjects.